Walk power mowers are well known for cutting grass. Such mowers are characterized by a relatively small mower deck, typically one that provides a 21″ cutting width, which is supported by four wheels at the corners of the deck for rolling over the ground. The underside of the deck typically includes a substantially circular cutting chamber. The cutting chamber houses a single rotary cutting blade that rotates about a substantially vertical axis in a substantially horizontal cutting plane. A small internal combustion engine or electric motor is laterally centered on top of the mower deck. The shaft of the engine or motor extends down through the top wall of the mower deck into the cutting chamber to be attached to the cutting blade.
Many mowers of this type have a rear bagging mode in which the grass clippings are thrown into and collected within a bag that is releasably fastened to the rear of the mower deck. In such mowers, the cutting chamber has a rearwardly extending discharge tunnel that progressively increases in height as it extends rearwardly to accommodate the grass clippings. The tunnel ends in a rearwardly facing grass discharge opening that is mated to the open mouth of the bag. Desirably, the tunnel and the bag are positioned so that they do not extend beyond the lateral sides of the deck to allow the mower to cut close to the sides of various structures, e.g. to cut all the way up to a flower bed, retaining wall or the like.
Mowers of the type noted above have conventionally been restricted to single bladed mowers having the aforementioned small cutting width. If the cutting width could be dramatically increased from say 21″ to 30″ or so, the user could cut 50% more grass on each cutting swath of the mower. This would greatly increase productivity by decreasing the amount of time needed to mow a particular area of grass. However, such a larger walk power mower could be stored in one's garage in much less space than that required for storing a riding mower. Thus, the ease of storage and greater productivity offered by a wide swath, walk power mower would be an attractive and less expensive alternative to a riding mower.
Attempts have been made to provide larger walk power mowers having a pair of side-by-side cutting blades that offer a wider cutting swath than a single bladed mower. However, such mowers have not provided a true rear bagging capability in the same manner as that provided by a single bladed mower with a rearwardly extending discharge tunnel. Such dual bladed mowers typically have discharged the grass clippings to the sides of the mower deck. The Applicants believe this to be the result of a belief in the art that the increased volume of grass clippings resulting from the operation of two blades could not be accommodated in a single rearwardly extending tunnel given the need to position the engine over the center of the deck in front of the bag.
Another difficulty posed by dual bladed mowers is the orientation of the cutting blades relative to one another. The two cutting blades are normally positioned in one of two different ways: 1.) the blades can be set generally side-by-side relative to one another but staggered fore and aft relative to one another so that their cutting orbits overlap one another in the middle of the deck but do not intersect with one another, or 2.) the blades can be set entirely or directly side-by-side relative to one another with no longitudinal staggering and with their cutting orbits intersecting with one another. With the latter approach, it is necessary to time the rotation of the dual blades relative to one another using a timing belt so that the dual blades do not hit one another as they rotate. A timing belt system requires fairly high belt tension to avoid the belt from coming off the cogged timing pulleys. Such high belt tension can warp or deform the fairly light mower decks typically used in these types of mowers.
Accordingly, it would be an advance in the art to provide a dual bladed walk power mower that would offer a true rear bagging mode and yet be durable and affordable.